Method and apparatus for detecting and localizing unwanted matter internally in a pipe string

ABSTRACT

A method and a device for detecting and localizing unwanted matter, e.g., cement deposits, internally in a drill string. A sleeve-shaped indicator body is dropped down through the drill string while the same occupies an operative position. Then, the indicator body lands either in a seat at the lower end of the drill string, or the indicator body becomes stuck within a pipe section at a higher level in the drill string. The drill string overlying the position of the indicator body may be considered free of deposits formed on the pipe section walls thereof, and these pipe sections thus may be re-used without any further examination or cleaning. If stuck at a higher level, the indicator body is subsequently localized at the surface through examination in context of disassembling the drill string. The indicator body also may comprise an indicator element that provides a detection signal or sign for its detection and localizing on the surface.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for detecting and localizingunwanted matter, such as deposited cement, contaminants, etc. internallyin a pipe string or tubing, preferably a drilling string of significantlongitudinal extent, consisting of drilling pipes, preferably drillcollars and a bit at the free outer end thereof, said method being basedon dropping a weight body narrower than the bore diameter, down throughthe pipe string.

Likewise, the invention relates to a device comprising auxiliary meansfor use upon detecting and localizing cement deposits and othercontaminant deposits within pipe strings and tubings having significantlength extent and composed of built up pipe sections/pipelengths/individual pipes.

2. Description of the Related Art

It is very important to have unwanted matter such as deposits and lumpslocalized and removed, from a pipe string which to a larger or smallerdegree clog or throttle the drilling string bore. These bore diameterreducing coating build-ups and deposits result often from previouspumping of cement through the drilling string.

Lumps of contaminating substances from circulated cement slurry couldrepresent a clogging phase if they land in the nozzles of the bit which,thus, become clogged or become so throttled that the circulation withinthe drilling string is influenced in a negative sense. Therefore, it isusual to “trip” (run in and pull out) the drilling string, test theindividual pipe sections in storage position in the derrick, and cleanthe pipe section(s) containing deposits and/or lumps, prior to a new runof the drilling string in the well can be carried out.

A drilling string consists of pipe sections screwed together, eachsection normally consisting of three pipes or pipe lengthsinterconnected through screwing. After each time's use of a drillstring, the screw connections between the individual pipe sections (alength of about 30 meters) are unscrewed. The pipe sections are usuallynot demounted into single pipes, but are stored on board the drillingplatform in their full lengths, uppermost engaging supportingly into afinger board up in the derrick, resting with their lower ends on thedrill floor. Within the derrick, at the level of the finger board, aperson sits in order to drop a ball or another heavy weight body downthrough each pipe section.

If said weight body falls through the respective pipe section withoutbeing stopped, the pipe section is considered to be internallynon-clogged and could be used for drilling again at a later point oftime without further treatment.

If the weight body, on the other hand, is stopped within a pipe section,this is a sign of the occurrence of internal deposits, and the pipesection has to be cleaned, possibly after having been dismounted intothe three pipe lengths thereof. Working in the derrick is associatedwith elements of risk, and this prior art detecting method isbothersome, troublesome and time-demanding. Each individual pipe sectionhas to be tested no matter what place it took in the drill string.

SUMMARY OF THE INVENTION

The method and the device according to the invention allow in mostcases, where no deposits occur, that one with certainty can assume thatthe entire drill string is sufficiently clean without having.to controleach and every pipe section.

The method according to the invention distinguishes itself through theuse of a sleeve-shaped/tubular indicator body with a smaller lateralmeasure than the diameter of the drill string bore and which, in situ,from a surface position is dropped down through the drill string,landing at a place further down within the drill string, said place, ata later stage, subsequently to disassembling the drill string, can bedetermined by testing the individual pipe sections, e.g., through ameasure indication from one end of the pipe section to the other, inconnection with the tripping in/storage of the individual pipe sectionson the drill floor.

The sleeve-shaped/tubular indicator body can be adapted to emitradioactivity, or it may be provided with an active radio chip adaptedto be detected by means of a magnetic field established outside thatpipe section which at any time is being examined in order to recover theindicator body and determine the place positioned at the highest level,referred to the drill string's position of use, where deposits occur.Then, at this highest positioned place within the drill string, thedeposits have stopped the further movement of the indicator bodydownwardly within the drill string, and above the determined highestpositioned place there are no internal deposits, coatings or otheraccumulations of cement or mud constituents, formation sand, etc. Assoon as one has positionally determined and recovered the indicator bodyand, thus, localized the pipe section exhibiting deposits, the remainingpipe sections which, thus, were positioned above that place within thedrill string where the indicator body was stuck, can be considered asdeposit-free internally. These pipe sections do not need any testing andmay immediately be stored for subsequent use in the next run of thedrill string. On the other hand, pipe sections which occupied positionswithin the drill string below said recorded deposit's “highest place”,may contain coatings. Therefore, the indicator body is dropped once moredown into the remaining part of the drill string.

At one end thereof, the end being the lowermost in the position of use,the indicator body may be formed with an external, conical, downwardlytapering stop portion. A special pipe piece having an externallythreaded socket at one end thereof and an internally threaded pin at theother end, is, thus, formed for interconnection with an overlying drillpipe of the drill string and an underlying drill collar of the same. Thespecial pipe piece has a stepped bore comprising two coaxial boreportions passing into each other through a short transition portionconnecting the upper bore portion, the diameter thereof agreeing withthe bore diameter of the overlying drill pipe, the latter diameterexceeding the diameter of an underlying bore portion which agrees withthe diameter of the underlying drill collar. In the transition betweenthe two longitudinal bore portions having different diameters, thisspecial pipe piece has an internal, conical, downwardly tapering seatwhich is substantially complementary to the external, conical stopportion of the indicator body at the lower end thereof.

The indicator body may, in situations where no deposits exist in theupper pipe sections of a drill string, be adapted to point this outimmediately after hauling the special pipe piece up in connection withthe drill string's pulling up (tricing), namely upon inspection of thespecial pipe piece as the first detecting/localization operation, inorder to ascertain whether the indicator body has landed in the seat ornot.

In order to remove the indicator body in case it has stopped in an areaof deposits, a tool may be used, said tool being lowered down into thepipe section. This hoisting tool may have the form of a U-shaped hoophaving somewhat resilient U-hoop legs in the plane of the legs and anupper, heavy web loading the tool with a weight. The tool is hoisteddown into the pipe concerned, suspended from a line attached to said webat the central point thereof. Laterally, the free outer ends of theU-hoop legs are directed away from each other. Internally, the indicatorbody has a circumferential groove in communication with the bore.

Uppermost, the indicator body may be formed with a conical, taperinginsertion aperture for guiding said U-hoop-shaped tool and temporaryclamping of the two, possibly three oppositely directed free outer endswhich, thereafter, resile out into engagement position in the area ofsaid internal circumferential groove, so that the upper faces on saidoutwardly directed, free outer ends of the U-legs engage in below thedownwardly facing face defining the internal circumferential groove fromabove, whereupon the indicator body can be hoisted up and used oncemore.

For localizing the pipe section of the disassembled drill string withinwhich the indicator body is positioned immediately, the indicator bodymay have one of two advantageous embodiments.

In one embodiment, the indicator body is provided with a cord having asmall plummet at the outer, free end thereof. The cord has such a lengththat a portion of it will project out from a pipe section's end if theindicator body itself has got stuck within a pipe section, irrespectiveof where in the pipe section the wedging of the indicator body didarise. The cord may e.g. have a length between indicator body andplummet of almost 30 meters.

In a second embodiment, a tubular indicator body according to theinvention has a length substantially corresponding to the length of thepipe section, i.e., about 30 meters, a wedging of this long indicatorbody anywhere in the pipe section concerned will cause an end portion ofthe tubular indicator body to project out from the upper end. Thissituation can be recorded as soon as the respective pipe section is inthe process of being pulled up. Overlying pipe sections of the pipestring can be considered as deposit-free without any need for internalcleaning.

A non-restricting exemplary embodiment of the uses and designs of theinvention appears from the attached drawings, wherein:

FIG. 1 shows an axial section through a lower portion of a is drillstring vertically orientated in the figure, and where a special pipepiece according to the invention is mounted in through interconnectionby screwing with partly an overlying drill pipe section, partly anunderlying drill collar;

FIG. 2 corresponds completely to FIG. 1 in respect of the drill stringportion, but here a sleeve-shaped/tubular indicator body, which has beendropped down through the drill string from a surface position, haslanded in the special pipe piece's seat with its complementarily shapedlower end;

FIG. 3 is a partial view showing an axial section through a pipe sectionand a therein stuck indicator body;

FIG. 4 corresponds to FIG. 3, but here a hauling tool has been lowereddown from a surface position, said tool being connected to the end of acord and serving to be brought into a firm engagement with an indicatorbody stuck within a pipe section, in order to haul it up by means of thecord;

FIG. 5 shows the indicator body separately in axial section;

FIG. 6 shows the pulling-up tool separately in side elevation view;

FIG. 7 shows a special embodiment in which, in the position of use, theindicator body, at the lower end thereof, is provided with a downwardlysuspended cord having a plummet at its lower end;

FIG. 8 shows a very long indicator pipe having a length corresponding toeach of the pipe sections (30 meters) included in the drill string, andin which this tubular indicator body/indicator pipe has been stuck atthe lower end of a pipe section.

DETAILED DESCRIPTION

First, reference is made to FIGS. 1 and 2, showing a partial view of adrill string, in which a special pipe piece 10 has been mounted inbetween and, at the ends thereof, screwed firmly to an overlying drillpipe/pipe section 12 and an underlying drill collar 14, respectively.

The special pipe piece 10 has an upper, central bore portion 16 having adiameter corresponding to the overlying pipe section's 12 bore diameter,and a lower bore portion 16′ extending coaxially with the upper boreportion 16 and having a smaller diameter, corresponding to the diameterof the underlying drill collar 14.

Between the bore portions 16 and 16′ of the special pipe piece 10, ashort transition bore portion 18 has been formed, forming an internal,conical, downwardly tapering seat.

A sleeve-shaped or tubular indicator body 20 having a through-going bore22, said body being shown separately in FIG. 5, has a lower, pointed endportion 20′ which is substantially complementary to the seat 18 of thespecial pipe piece 10. The indicator body 20 exhibits an internal,conical, downwardly tapering guide face 20″ at the upper end thereof andis, below the same, formed with an internal circumferential groove 20′″communicating with the bore 22.

The sleeve-shaped indicator body 20 has an outer diameter somewhatsmaller than the bore diameter of the pipe section 12 and exceeding thebore diameter of the drill collar 14. The lower conical end portion 20′is, as mentioned, complementary to the seat 18 in the special pipe piece10, and these will get in engagement, FIG. 2, in cases where theindicator body 20 which has been dropped from a surface position, fallswithout hindrances through all overlying pipe sections, of which thepipe section 12 is the lowermost. Below the drill collar 14, only drillcollars exist down to the bit.

If one, when carrying out a method for detecting and localizing internaldeposits, ascertains that the indicator body 20 has landed in the seat18, this indicates unambiguously that all overlying pipe sections of thedrill string are free of cement deposits or other unwanted deposits.Thus, these pipe sections 12 do not need to undergo further inspectionwhen the drill string has been pulled up and disassembled for storage ofthe individual pipe sections on the drill floor and in the finger boardin the derrick.

The drill collars 14 below the special pipe piece 10 of the drill stringshould in any case be examined in order to detect and localize cementdeposits, etc. and, possibly, cleaned prior to the next time's run ofthe drill string. Such examination can be carried out in the same mannerby using an indicator body 20 having a smaller diameter.

When the indicator body 20 has landed in the internal seat 18 in thespecial pipe piece 10, it is easy to get the indicator body 20 broughtout of the pipe piece 10.

If the indicator body 20 has gotten wedged or in some other way has beenstuck in internal deposits 26 in a pipe section 12, see FIG. 3, theindicator body 20 may have been stuck in the middle portion of a pipesection, from where the distance is about 15 meters to each end.

In accordance with the present invention it is, therefore, designed asimple withdrawal tool 28 to enable withdrawal of the indicator body 20when the pipe section 12 a concerned has been placed on the drill floorin connection with the disassembling of the drill string.

The withdrawal tool 28 is suspended from a hoisting cord 30 and isformed as a U-shaped hoop, the legs thereof being resilient toward andaway from each other. The web is relatively thick and heavy, forming afastener at a through-going lateral hole for said hoisting cord 30. Theouter, free ends 28′ of the U-hoop legs are bent about 90°, pointingaway from each other.

When the withdrawal tool 28 is lowered down into the indicator body 20,the outer, free ends 28′ come into guided, inwardly displacing contactwith the upper, funnel-shaped aperture 20″, such that the free outerends 28′ of the resilient U-hoop legs are kept in this inwardly pressedposition of readiness until they a short time afterwards are positionedat the same level as the internal circumferential groove 20′″, intowhich the free outer ends resile and establish a firm and secureengagement. Thereupon, it only remains to pull the cord 30 upward,whereby the withdrawal tool 28 and the indicator body 20 accompany thesame and eventually are removed from the pipe section which, thus, iscleaned and freed from the deposits 26.

Thereupon, the indicator body 20 is once more dropped into the remainingpart of the drill string, and the operation is repeated until theindicator body has landed in the special pipe piece 10.

In FIGS. 7 and 8, two advantageous embodiments are shown.

In the embodiment of FIG. 7, where a sleeve-shaped indicator body 20 hasbeen stuck in underlying deposits 26 within a pipe section 12, the lowerend of the indicator body 20 is provided with an indicator cord 32having a small plummet 34 at the end thereof. The cord 32 has alongitudinal extent exceeding a pipe section'approximately, 30 meters,to allow the plummet 34, by means of the cord 32, to project out fromthe closest underlying pipe section end in case the indicator body 20has become stuck in deposits. In most cases, the pipe section bore isnot so fouled with deposits that it is entirely clogged, prohibiting thepassage of the cord 32 and the plummet 34 in a downward direction. Thepipe section in which the indicator body 20 might have got stuck, will,during tripping, immediately be detected based on the fact that the cord32 with the plummet 34 is visible below the lower portion of the drillpipe 12.

In FIG. 8 is shown a particular embodiment for a tubular indicator 20Ahaving a length corresponding to the length of a pipe section, i.e.about 30 meters. Irrespective of where in the pipe section 12 thistubular indicator body 20A has got stuck, an end portion thereof willproject outside an end of the pipe section 12 and, immediately, detectand localize the lowermost pipe section of the drill string exhibitingdeposits 26 to be removed. As a consequence of the indicator body's 20Aconsiderable weight, any deposits would normally be cleaned away duringthe displacement of the indicator body 20A through the drill pipes 12.If the indicator body 20 is treated with a radioactive substance or insome other way enabled to emit radioactivity, possibly provided with anactive radio chip, the indicator body 20 could be detected during thetripping by means of an external detector located on the drill floor.Preferably, the indicator body 20 should be provided with a bore 22, sothat drill fluid can be circulated within the well also after theindicator body has been dropped down.

What is claimed is:
 1. A method for detecting and localizing unwantedmatter within pipe sections and drill collars included in a drillstring, comprising: dropping a tubular indicator body from a surfaceposition down through the drill string, said indicator body having aninsignificantly smaller external diameter than the bore diameter of thedrill string, the indicator body landing either in a seat at the lowerend of the drill string or being stopped and retained by unwanted matterwithin a pipe section higher up in the drill string; and when said drillstring is subsequently disassembled, and prior to re-use in a drillstring, examining individual pipe sections to localize the indicatorbody position, the localizing thereof indicating that its pipe sectioncontains unwanted matter, and that overlying pipe sections are free ofsaid unwanted matter formed on the internal walls thereof.
 2. A devicefor detecting and localizing unwanted matter within pipe sections anddrill collars included in a drill string, comprising: a pipe piece whichis formed with an internal seat, and which is mounted within the lowerend of the drill string; and a tubular indicator body having athrough-going bore and a lower end stop portion adapted to engage saidseat within said pipe piece of the drill string, the indicator body alsohaving an insignificantly smaller external diameter than the borediameter of the drill string, and the indicator body being configured tobe dropped into the drill string from surface and landing either in saidseat at the lower end of the drill string or being stopped and retainedby unwanted matter within a pipe section higher up in the drill string,wherein the tubular indicator body comprises an indicator element whichis detectable from outside a pipe section when said drill string issubsequently disassembled, the detection and localization of theindicator body within an individual pipe section indicating that thepipe section contains unwanted matter, and that overlying pipe sectionsare free of said unwanted matter formed on the internal walls thereof.3. The device of claim 2, wherein said tubular indicator body has alower, tapering end adapted to fit within a complementary shapedinternal seat of said drill string pipe piece and wherein said seat hasan upper diameter corresponding to an overlying pipe section's borediameter and a lower diameter corresponding to an underlying drillcollar's bore diameter.
 4. The device of claim 3, wherein the indicatorbody has an upper tapering inlet portion having an upper diametersubstantially corresponding to an overlying pipe section's borediameter, and having a lower transition portion having a diametersubstantially corresponding to an underlying collar's bore diameter. 5.The device of claim 2, wherein the indicator body has an internalcircumferential groove to enable its withdrawal from the pipe string. 6.The device of claim 2, wherein said pipe piece is formed with threadedend portions for interconnection by screwing with coaxial, threaded endportions of drill pipes or collars.
 7. The device of claim 2, whereinthe seat forms a transition portion between an upper bore portion, thediameter thereof corresponding to the overlying pipe's diameter, and anunderlying, narrower bore portion, the diameter thereof corresponding toan underlying pipe's bore diameter.
 8. The device of claim 2, whereinthe indicator element emits radioactivity in order to detect andlocalize the indicator body.
 9. The device of claim 2, wherein theindicator element comprises a plummet which depends therefrom on anindicator cord in order to detect and localize the indicator body. 10.The device of claim 2, wherein the indicator body has the form of anelongated pipe, having a length substantially corresponding to thelength of the pipe section, so that an end portion of the indicator bodyprojects out from the end of the pipe section upon the disassembly ofthe pipe string.
 11. The device of claim 2, additionally comprising awithdrawal tool for withdrawing the indicator body from a pipe sectionafter the indicator body is dropped into the drill string containing thepipe section, wherein the withdrawal tool comprises a U-shaped hoophaving resilient legs adapted to releasingly engage the indicator body,and wherein the hoop has a hoisting cord attached thereto.
 12. Thedevice of claim 2, wherein the indicator element comprises an activeradio chip which emits radio signals in order to detect and localize theindicator body.
 13. A device for detecting and localizing unwantedmatter within pipe sections and drill collars included in a drillstring, comprising a pipe piece formed with an internal seat and mountedwithin the lower end of the drill string, and also comprising a tubularindicator body having a through-going bore and a lower end adapted toengage said seat within said pipe piece, and wherein the indicator bodycomprises an indicator element which emits radioactivity in order todetect and localize the indicator body.
 14. A device for detecting andlocalizing unwanted matter within pipe sections and drill collarsincluded in a drill string comprising a pipe piece formed with aninternal seat and mounted within the lower end of the drill string, andalso comprising a tubular indicator body having a through-going bore anda lower end adapted to engage said seat within said pipe piece, andwherein the indicator body has the form of an elongated pipe having alength substantially corresponding to the length of the pipe section, sothat an end portion of the indicator body projects out from the end ofthe pipe section upon disassembling the drill string into individualpipe sections.
 15. A device for detecting and localizing unwanted matterwithin pipe sections and drill collars included in a drill string,comprising a pipe piece formed with an internal seat and mounted withinthe lower end of the drill string, and also comprising a tubularindicator body having a through-going bore and a lower end adapted toengage said seat within said pipe piece, and wherein the indicator bodycomprises an indicator element comprising a plummet which depends fromthe indicator body on an indicator cord in order to detect and localizethe indicator body.
 16. A device for detecting and localizing unwantedmatter within pipe sections and drill collars included in a drillstring, comprising a pipe piece formed with an internal seat and mountedwithin the lower end of the drill string; and also comprising a tubularindicator body having a through-going bore and a lower end adapted toengage said seat within said pipe piece, and wherein the indicator bodycomprises an indicator element comprising an active radio chip whichemits radio signals in order to detect and localize the indicator body.17. The device of claim 2, wherein said tubular indicator body has alower, tapering end adapted to fit within a complementary shapedinternal seat of said drill string pipe piece.
 18. The method of claim1, additionally comprising removing said indicator body from unwantedmatter in a pipe section and dropping said indicator body into aremaining section of the drill string to test for additional unwantedmatter therein.